How to Care for St. Augustine Grass

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Anyone who has spent time in warm coastal areas of the South should be familiar with Stenotaphrum secundatum. In Australia and South Africa, they call it Buffalo turf. In South Carolina, it is called Charleston grass. But in Florida and most of the United States, we know it as St. Augustine grass.

This native North and Central American species naturally occurs on beach ridges, swamp edges, and limestone shorelines. It is one of the most popular lawn grasses for mild coastal areas all over the world. Although it does not withstand the high traffic of golf courses and athletic fields, St. Augustine is the most shade tolerant of the warm-season species. Homeowners love its attractive broad, flat leaf blades, dense foliage, and dark green color. In this guide, we’ll uncover the secrets to growing a strong, healthy St. Augustine grass lawn.

Where to Grow St. Augustine Grass

St. Augustine lives in USDA zones 8 through 10, from the Carolina Coast across the Gulf Coast region and Southern California. It grows in a wide range of soil conditions, from sand to clay, thrives in heat and humidity, and displays good drought tolerance and excellent salt tolerance. But it does not tolerate saturated or wet soil. Although most cultivars, including widely planted ‘Floratam,’ need eight hours of direct sunlight, ‘Seville’ and ‘Delmar’ only require six. So, St. Augustine is a good choice for all but the shadiest or wettest lawns.

Since seeds are not available, the only way to start a new St. Augustine lawn to install sod or plugs. The best time to plant is in early to mid-summer, four to six weeks before the end of the growing season. Remove any existing vegetation and till the area to prepare it for installation. Water the sod well after installation.

Watering

This grass needs about 1.5 inches of water per week during the growing season. When rain is sufficient, do not irrigate. If it’s not raining, run the sprinklers twice a week to apply .75 inches of water each time. Only water during the dormant season if you get no rain in a month.

Rather than scheduled irrigation, the best way to determine the water requirement for St. Augustine grass is by observing it. During the growing season, it may take on a dry appearance and a blue-green color, indicating that it is thirsty. When this happens, water the following morning. Another way to tell if the lawn is dry is by walking on it. If the blades spring back, there’s no need to water. If they remain flattened, water the following morning.

Fertilization

Fertilization should be done according to soil test results. Submit soil samples to your local Cooperative Extension Service in late spring. You’ll receive results within six weeks. Do not apply fertilizer until the weather is consistently warm and the grass is fully green.

St. Augustine absorbs and uses nutrients most efficiently when the soil is within the ideal pH range of 6.0 to 6.5. Use pelletized sulfur at a rate of 5 pounds per 1,000 square feet to decrease the pH if necessary. The grass will use between 2 and 4 pounds of actual nitrogen per 1,000 square feet annually. If the pH is correct, but the blades has a yellow cast, it may need an iron supplement as well.

The soil test results include annual nutrient requirements. Divide the total recommended fertilizer amount and make three applications, one each in mid-May, early July, and at the end of August.

Use fertilizer that has a high nitrogen content. An N-P-K ratio of 4-1-2 is generally a good ratio unless your soil test suggests otherwise.

St. Augustine lawn that has healthy turf blades
Photo credit to Jay Morgan

Mowing

Mow at a height between 2.5 and 4 inches, as frequently as necessary to remove no more than one-third of the height per cut. Allowing the it to grow too tall between mowing risks damage to the stolons at the following cut. When the grass is growing quickly in early summer, it may be necessary to mow every 5 days, but once a week is generally sufficient. In early spring, mow and bag the clippings once or twice at a height one notch lower than normal to remove old brown foliage.

Thatch buildup sometimes becomes problematic in St. Augustine lawns. If the buildup reaches a half-inch thick, it should be dethatched. Use a dethatcher or a vertical mower to remove the buildup shortly after spring green up. That is also the best time to aerate the soil if needed. Dethatching and aeration improve the grass’s ability to maintain a thick, dense sod that crowds out weeds.

Weed Control

Weed control starts with proper maintenance. Ensuring the best possible environment for growing St. Augustine gives it a competitive edge over weeds. Maintain good fertility, adequate soil moisture, and proper mowing height. Prevent annual summer weeds like crabgrass and goosegrass by applying pre-emergent weed killer in late winter, and again 8 to 10 weeks later. Spot spray summer and winter weeds with liquid post-emergent weed killer only when the lawn is fully green and growing or fully dormant – not during the spring or fall transition period.

Pests and Diseases

Well maintained grass has few insect and disease pests that cause real damage. Watch for mole crickets and chinch bugs in late spring. Both are attracted to dry lawns with heavy thatch buildup. Mole crickets create mounds of soil where they burrow, and the soil may become spongy before the grass begins to dieback. They cause the grass to brown out in one area, then begin to move across the yard in a visible progression. Treat these problem insects with a liquid or granular lawn insecticide.

Brown patch fungus can infect St. Augustine grass when humidity is high, daytime temperatures are mild, and nights are cool. It appears as one or more large brown patches of grass, each with a telltale orange-ish “smoke ring” around the perimeter. The patches can quickly spread and merge. Treat brown patch with a lawn fungicide. Also, stop watering and do not fertilize while brown patch is active. Bag and dispose of the grass clippings when you mow these areas of the lawn.

St. Augustine grass makes a beautiful, moderate-maintenance lawn for mild climate areas. Although it is not a great choice for parks or sports fields, it is one of the best for private homes where foot traffic is light. It offers soft, dense, dark green foliage that feels good on bare feet and looks great in any landscape, with very few pest problems. It’s no wonder that this native North American turfgrass is one of the most popular lawns where it lives.

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About the author: Mark Wolfe is a lawn care expert and arborist with more than 20 years experience in the landscaping and nursery sector.

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